KAZALD1 (Kazal type serine peptidase inhibitor domain 1) functions as a regulatory protein with diverse roles in tissue homeostasis and disease progression. In cartilage biology, KAZALD1 maintains cartilage homeostasis by attenuating chondrocyte fibrosis through interference with pro-fibrotic TGF-β signaling 1. Mechanistically, KAZALD1 forms a dimer with TGFBR1, blocking the TGF-β1-Akt/Smad3 signaling pathway and suppressing fibrotic gene expression 1. However, KAZALD1 demonstrates contrasting roles in different pathological contexts. In glioma, KAZALD1 acts as an oncogene where promoter hypomethylation leads to overexpression, promoting malignant progression through enhanced cell proliferation and invasion 2. Similarly, KAZALD1 is upregulated in osteosarcoma and serves as a survival-related biomarker associated with poor prognosis 34. Single-cell RNA sequencing studies reveal that KAZALD1 is highly expressed in cancer-associated fibroblasts and osteoblastic osteosarcoma cells 4. In malignant pleural mesothelioma, KAZALD1 undergoes epigenetic silencing through DNA hypermethylation, serving as a potential diagnostic marker 5. The protein also shows promise as a biomarker for diabetic nephropathy 6. These findings highlight KAZALD1's context-dependent functions, acting as either a protective factor in cartilage or promoting malignancy in various cancers.